The financial advisor is NOT using percentages properly, because the 60% increase would multiply the new value after one year, and not the initial value.
So first let's find the investment after one year:
[tex]\begin{gathered} 10000-50\text{\% of 10000} \\ =10000-0.5\cdot10000=10000-5000=5000 \end{gathered}[/tex]Then, we have an increase of 60%, so:
[tex]\begin{gathered} 5000+60\text{\% of 5000} \\ =5000+0.6\cdot5000=5000+3000=8000 \end{gathered}[/tex]The final value is 8000, which is lesser than the original value, so we have a loss.
The percentual loss is:
[tex]\frac{10000-8000}{10000}=\frac{2000}{10000}=0.2=20\text{\%}[/tex]